This invention relates to piston pumps and compressors, and more particularly to a compressor head assembly with an integral pressure relief valve assembly.
Small-scale air compressors are often used to power nebulizers. A typical type of compressor for that purpose uses a wobble piston. Examples of such compressors are found in U.S. Pat. No. 3,961,868, issued Jun. 8, 1976 to Arthur J. Droege, Sr. et al, for "Air Compressor" and U.S. Pat. No. 4,842,498, issued Jun. 27, 1989 to Roy J. Rozek, for "Diaphragm Compressor".
In a typical compressor, a piston reciprocates in a cylinder sleeve to compress air. The piston is a plastic connecting rod having a piston end disposed in the cylinder sleeve, and a connecting end connected to an eccentric metal pin mounted to a shaft. As the shaft rotates, the connecting rod having a piston head disposed in a cylinder sleeve reciprocates to compress air. The compressed air escapes from the cylinder sleeve through an exhaust port into a valve head member.
When the exhaust outlet on the valve head member is blocked, pressure builds up in the cylinder sleeve which can cause the compressor assembly to overheat, stall, or potentially trip the motor thermal protector, failing the compressor unit. It is known to provide a pressure relief valve assembly in fluid communication with the exhaust port in order to provide a fluid passage when fluid pressure exceeds a predetermined relief setting.
These known relief valves are typically machined out of brass or similar materials to define a passage. The passage is blocked by a poppet disposed therein. The poppet is held in place by a spring compressed by a knob. The knob has conventional external threads which engage internal threads cut into the passage to compress the spring.
Providing a relief valve formed from brass is expensive. Furthermore cutting threads in the passage adds to the cost, and increases the time required to assemble the relief valve. Therefore, a need exist for a pressure relief valve assembly which is inexpensive and easily assembled.